Double cylinder hand pumps have been generally known to the art for some time, yet their application to high volume, low pressure inflatable products has not been fully realized.
No known provision exists to take advantage of the fact that 75% to 85% of inflated air by volume of a given product, such as an air mattress, or life raft, or the like, is inflated at extremely low pressures, where user could easily increase the volume of air pumped while not exceeding a reasonable effort on behalf of the user.
There are no known hand operated pumps that take advantage of increasing the volume of low pressure air, while providing for a decrease in volume of higher pressure air, to provide for optimizing pumping pressure during the entire inflation cycle without exceeding a predetermined maximum pumping effort.
The uneven distribution of pumping effort of other pump results from designing a pump to supply a given inflation pressure with a given maximum pumping effort, by specifying a fixed piston area, without taking into account that more than half the volume of air is pumped at low pressure. The extra inflation time was not significant while inflating small products such as beach balls or bicycle innertubes, but with larger inflatable products, much time and effort is expended during inflation.
By providing a means to separate pumping action, the size of the piston area can be doubled while pumping pressures are low and the piston area can be reduced in half when increased inflation pressures effect an increase in pumping force, resulting in a large reduction of strokes required to inflate a given object, and a shortening of overall inflation time.